Artículos de Reflexión

Postoperatory Venous Thromboembolism: A Serious Preventable Risk

 

Tromboembolismo venoso postoperatorio: grave riesgo prevenible

 

Wilson Valencia A.*, Johnnie Smith Husbands Luque**

* Médico Anestesiólogo Universidad del Valle. Profesor Facultad de Medicina Universidad Santiago de Cali. Anestesiólogo Hospital San Juan de Dios, Cali, Colombia. wilsonvalenciaa@hotmail.com

** Médico Anestesiólogo Universidad Nacional de Colombia. Profesor Facultad de Medicina Universidad Libre Seccional Cali. Instructor Reanimación AHA BLS ACLS Fundación Reanimación Colombia - SCARE. Anestesiólogo Clínica Nuestra Señora de los Remedios, Clínica Rafael Uribe Uribe, Cali, Colombia. jshusbands@hotmail.com

Recibido: mayo 27 de 2010. Enviado para modificaciones: julio 26 de 2010. Aceptado: octubre 2 de 2010.

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Summary

Postoperative deep venous thrombosis and pulmonary thromboembolism are complications which have incidence on morbimortality. Many researches evidence their figures and how thromboprophylaxis can reduce these risks. Different drugs and their level of protection have been evaluated, but the adherence to the published clinical practice guidelines is not optimal because of the lack of clarity in the management of patients with intermediate risk factors. The proved prevention with thromboprophylaxis forces to implement strategies to detect the patients at risk and to follow the guidelines.

Keywords: Thrombosis, embolism, risk, prophylaxis. (Source: MeSH, NLM).

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RESUMEN

La trombosis venosa profunda y el tromboembolismo pulmonar postoperatorio son complicaciones que tienen influencia en la morbimortalidad. Múltiples investigaciones evidencian sus cifras y la reducción del riesgo con la tromboprofilaxis. Han sido evaluados diferentes medicamentos y su nivel de protección, pero el seguimiento de las guías de práctica clínica publicadas no es óptimo debido a la falta de claridad en el manejo de pacientes con factores de riesgo intermedio. La prevención demostrada por la tromboprofilaxis obliga a implementar estrategias para detectar pacientes en riesgo y seguir las guías.

Palabras clave: Trombosis, embolismo, riesgo profilaxis. (Fuente: DeCS, BIREME).

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Introduction

During the postoperative period (POP) patients may develop deep venous thrombosis (DVT) and pulmonary thromboembolism (PTE), entities known as venous thromboembolism (VTE), which are consequences of a hypercoagulable state due to stasis, and to the activation of platelet aggregation and coagulation factors by the contact of the vascular subendothelial collagen and tissue phospholipids with the plasma. It is the third cause of postoperative death, and postoperative PTE is the leading cause of preventable death (1). The purpose of this article is to make a reflection around the existing literature about the subject, in the framework of the clinical practice guidelines –to which the adherence is not optimal–, and make a proposal on the adoption of some strategies to detect the patients and follow the guidelines.

State of the art

The risk of DVT POP when prophylaxis is not carried out is between 3 and 80 %, most of them having an asymptomatic course (1-3). Motte et al (3) found in 2006 that the incidence of postoperative DVT in general surgery in patients without prophylaxis is 19 %, thromboembolism occurring in 1.6 % and fatal PTE in 0.2-0.9 %. If the surgery involves cancer, the incidence of asymptomatic DVT is 29 %. In gynecologic surgery it ranges between 4 and 38 %, in total hip replacement (THR) it can be up to 57 %, with letal PTE of 0.1-3 %. Surgeries of hip fractures show figures of fatal PTE between 2.5 and 7.5 %. In total knee replacement (TKR) DVT occurs between 41 and 85 %, with fatal PTE between 0.1 and 1.7 %. In neurosurgery it was found an incidence of asymptomatic postoperative DVT between 24 and 33 %.

Sweetland et al (4) found that of 239,614 women who underwent surgery, 5,419 developed VTE, cause of 270 deaths, 40 times more than in non-surgical patients. In the first week the relative risk (RR) was 40.3, (CI 95 % 30.7-52.8), with an increase to 110 times in the third week (RR 112.5, CI 95 % 95.3-132.8). The RR was 69.1 (CI 95 % 63.1-75.6) in the first six postoperative weeks and 19.6 (CI 95 % 16.6- 23.1) between the weeks 7 and 12.

The very fact of being hospitalized predisposes to the development of DVT (5). The risk increases with comorbities. Mantilla et al (6) found as a risk factor a level equal to or greater than 3 in the ASA preoperative physical status classification (p = 0.002), RR 2.6, (CI 95 %: 1.4-4.7).

The risk factors associated with the development of VTE include: previous DVT or PTE that suggest hypercoagulability syndrome, hip or pelvic surgery, presence of cancer, age over 60 years, immovility equal to or longer than four days, obesity (BMI > 30), therapy with estrogens, pregnancy, smoking, varicose veins of lower extremities, inflammatory bowel disease, nephrotic syndrome, sepsis, etc. (1,3,6). The extent of the surgery influences the risk; for example, the incidence of VTE in herniorraphies is low: 0.04 % (1).

There is controversy about the lower risk of DVT POP when conductive anesthesia is used compared to when general anesthesia is employed. Sharrok et al analyzed the data of patients who underwent major orthopedic surgery between 1986 and 1995, and they did not find any difference between the two types of anesthesia (6).

The American College of Chest Physicians (ACCP) published in 2008 the eighth edition of their clinical practice guidelines (CPGs) for the prevention of postoperative VTE. There are classified three risk groups (see table 1), according to the magnitude of the surgery, model which is similar to that of the European schemes that determine the risk by conjugating factors of the surgery with those of the patient (3).

Prevention begins with the patient education. It is recommended to use mechanical measures to reduce stasis, such as, for example, early deambulation. Continuous compression stockings and intermittent compression (IC) devices are the most studied methods; a decrease of postoperative DVT from 19 to 7 % has been reported, when these are used in general surgery, and when associated with pharmacological measures, the outcomes improve (1).

Pharmacological thromboprophylaxis reduces the incidence of VTE between 60 and 72 %, and of fatal PTE by 64 %. The recommended medications are:

• Conventional heparin (recommendation class I): in general surgery it reduces the incidence of fatal PTE from 0.71 to 0.21 %. It may produce surgical wound hematoma in 4.1-6.3 % of cases (1,3), and thrombocytopenia in 2-3 %.

• Low molecular weight heparins (LM WH) (class I): they prevent VTE similarly to the CH, but they induce thrombocytopenia only in 0.1 % of cases.

• F F ondaparinux, synthetic pentasaccharide inhibitor of factor Xa (class I): it prevents VTE POP in the same way as the LMWH, with minimal side effects (1,3).

• Oral inhibitors of factor Xa such as rivaroxaban (7,8): approved for use by the FDA in 2009, therefore they do not appear in the CPGs of the ACCP.

• Direct thrombin inhibitors such as dabigatran, Oral use: they offer protection similar to the LMWH. Approved for use by the European Medicine Agency in 2009 (5); they do not appear in the CPGs of the ACCP.

• Warfarin: it can be used in high-risk patients (class IIa), but it is associated with major POP bleeding of up to 5 %, and it requires laboratory monitoring.

• Aspirin: its effectiveness in prevention has consistently demonstrated to be lower than that of other thromboprophylaxis systems, for this reason the ACCP does not recommend its use.

In 1997 the FDA reported 41 cases of spinal hematoma associated with the use of LMWH (9), most of them occurred in patients with traumatic or multiple punctures. As for the use of heparins, the ACCP recommends to refrain from performing spinal punctures or removing catheters until 12 hours after their administration. If a puncture or catheter removal is performed, it is necessary to wait two hours before applying them. Catheters should not be left in the epidural space for more than 24 hours, nor punctions should be performed in those patients who are receiving anticoagulation via IV, have taken thrombolytic agents in the last 10 days or clopidrogel in the last week. Aspirin is not associated with risk of spinal hematoma.

Prophylaxis can be initiated before or after surgery (10). It has been demonstrated that the risk encompasses several POP weeks and the prophylaxis should be extended, primarily in patients at special risks (4,5,11,12). The asymptomatic cases can be reduced twice or three times more with prophylaxis for up to three weeks. Symptomatic DVT appears on average 17 days after HTR, and the incidence remains high for up to two months.

The recommendations of the ACCP 2008 are summarized in table 2. For all of this the level of recommendation is class I. When there is a high risk of bleeding, only mechanical measures will be used and pharmacological thromboprophylaxis will be started if that risk disappears.

Discussion

VTE is a clearly established postoperative complication. There is irrefutable evidence that prophylaxis significantly reduces the morbimortality. Even so, the adherence to the CPGs is not as expected (4,5). In 1986, only one third of the patients at risk received prophylaxis. Kakkar et al (2) found that of 92.5 % of the patients operated on between 2006 and 2007 who were at risk for VTE, 37.7 % did not receive the recommended prophylaxis. The acceptance of new CPGs for the prevention of postoperative VTE has special difficulties, because in some aspects, they are not concrete.

• The difference between minor and major surgery is subjective. The ACCP defines as major surgery, without specifying, the majority of general, gynecologic and urologic open surgeries, and thereby it generates uncertainty about prescribing thromboprophylaxis in patients with intermediate risks, or in open surgery patients but without special risks.

• The recommendation to prescribe prophylaxis until the discharge from the hospital is not concrete. Such broad margins of time (from the hospital discharge up to 28 days, between 10 and 35 days) produce insecurity. This variation is supposed to be determined by the existing risk factors, but concrete parameters are not described.

• Some authors consider uncertain the relationship between asymptomatic DVT and the development of significant embolisms. Most published studies seek cases of VTE and not clinical cases. There is a relationship between the asymptomatic cases and morbimortality, but its magnitude is not clear (3).

• There are different perceptions of the risk magnitude. The American Academy of Orthopedic Surgeons establishes that there are few studies linking the development of DVT with PTE, and that pharmacological thromboprophylaxis causes significative postoperative bleeding in a higher rate than the described in the published studies (13). Its recommendations suggest to prevent only the symptomatic PTE.

• Open surgery patients will receive pharmacologic prophylaxis, recommendation based on multiple studies that establish the risk, but globally, without discriminating concrete models.

Thus, although we have available CPGs, there is uncertainty about the types of surgeries which require thromboprophylaxis and its duration. For this reason, VTE remains the leading cause of preventable postoperative mortality.

As a consequence, the following proposals can be made.:

• To follow the CPGs of the ACCP, as there is enough quantity and quality of evidence demostrating a significant reduction of mortality secondary to postoperative VTE with the practice of thromboprophylaxis, and fatal PTE may be its first manifestation. This is more efficient that to treat the already clinical cases. The differences between the time proposed for prophylaxis, the uncertainty related with the different magnitudes of surgeries and with the association of symptomatic or asymptomatic nature of the DVT with the embolic episode, will be resolved by conducting studies that allow to have a more concrete panorama.

• Hospitals should implement strategies for the knowledge and prevention of VTE, as recommended by the ACCP. This has been promoted by programs which seek excellence in quality. The Surgical Care Improvement Project, of the American Medical Association and Government Agencies of the United States, seeks to reduce surgical complications in that country by 25% during the period comprised between the years 2005 and 2010 (5), and has intervened in processes to improve VTE prophylaxis. Computerized systems that warn about the existence of risks and allow to evaluate the need for prophylaxis have been used.

• In Colombia it is necessary to create commitees for the prevention of postoperative VTE and implement strategies to detect the risk and the necessity of thromboprophylaxis, through automated or manual systems, and thus, forgettfulness or misperception of the risk can be avoided. As well, multidisciplinary research groups should be created, in order to have own statistics and contribute to the adequation of the CPGs.

 

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13. American Academy of Orthopedic Surgeons. Clinical Guideline on Prevention of Symptomatic Pulmonary Embolism in Patients undergoing Total Hip or Knee Arthroplasty. Available from http://www.aaos.org/Research/guidelines/PE_guideline.pdf. released may, 2007. Last accessed: April 19, 2010.        [ Links ]